stress devitor (sheart stress) for mirror particles, thanks

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stress devitor (sheart stress) for mirror particles, thanks

hi every one, I am studying SPH, and focusing on Fortran programs these days, and here i have questions about mirror particles.
Application of mirror particles is of great significance in simulation of rigid surface, and i know the physical variables for a mirror particle is symmetrical with corresponding particle's.Consequently, both of them have the same value for mass, density, sound, internal energy, and hydrostatic pressure, and have opposite values for velocity in symmetrical derection. But how about stress deviator or shear stress, i am not sure for the equation for them.
Supposing a simulation in 2D condition, mirror particle J correspond with particle I in Y axis. ST XX(J) represents the stress deviator in x derection of parcile J.Would you help me to find out the equation of stress deviators between them? Which of following formulation is correct?
ST XX(I)= ST XX(J)
ST YY(I)= -ST YY(J)
ST XY(I)= ST XY(J)

or

ST XX(I)= ST XX(J)
ST YY(I)= -ST YY(J)
ST XY(I)= -ST XY(J)
thank you so much.
chibi1206

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Joined: Wed Jun 22, 2011 8:32 am 